This invention relates to mechanisms and, more particularly, to an improved detent for a mechanical linkage.
One type of detent for a mechanical linkage is engaged as the linkage moves into a locked position and is disengaged as a force is applied to the linkage that is greater than the normal moving force, i.e., the moving force when the detent is not engaged. A well known application of this type of detent is the mechanism for holding a car door in its open position, which comprises a roller and a spring-loaded pivot arm with one or more arcuate recesses. As the car door opens, the pivot arm moves across the roller until the roller drops in a recess, which locks the car door in the open position. To disengage the detent, sufficient force must be applied to the car door to move the pivot arm against the spring loading until the roller is "lifted" out of the recess. This same spring loading, which serves the desired purpose of holding the door in the locked position, prematurely forces the car door into the locked position during opening as soon as the roller begins to enter the recess. As a result, the car door moves out of control of the person opening it a distance that is greatly magnified at the unhinged edge of the car door. On the other hand, if too little spring loading is employed, the car door may accidently slip out of the locked position, causing personal injury. Approximately the same unlocking force is required to close the door as to open it from a locked intermediate open position to a fully open position -- thus, the door either opens with too much difficulty or closes too easily, depending upon the spring loading selected.